of detroit



Ngv. 22, 1932.

M. A. POWERS 1,888,695

OIL BURNER IGNITION DEVICE led July l, 1931 WARM,

I Patented Nov. 22, 1932 UNITED STATES-- PATENT? orr ca MILTON A. I'O'WERS, OF DETROIT, MICHIGAN, ASSIGNOR TO THE TIMKEN SILENT AUTOMATIC COMPANY, OF DETROIT, MICHIGAN, A CORPORATION OF MICHIGAN OIL BURNER IGNITION DEVICE Application filed July 1, 1931. semi in. 548,094,

My invention relates to oil burner ignition systems, particularly ignition systems of the spark type. for burners wherein ignition takes place around the periphery of a ring at the outer margin of a hearth member, fuel and air being sprayed to said combustion zone. The invention has for its principal object an electrode that will properly ignite the fuel under all service conditions and that will not become short-circuited by an accumulation of carbonat or near the spark gap. It also providesan ignition system substantially free from radio interference, a portion at least of such freedom being directly attributable to the maintenance of an at-,

mosphere partially composed of hydrocarbon vapors surrounding the intensely hot ignition are. The invention consists in an igniter having one elongated ribbon-like electrode of substantial width'and comparative-- 1y little thickness disposedso as to intercept a portion of the air stream and direct it to the spark gap, thereby creating oxidation conditions that prevent accumulation of carbon in the vicinity of the spark gap. It also consists in an electrode shaped to allow the are to move over a portion of its surface under outside influences. The invention further consists in theoil burner ignition devices and in the parts and combinations and arrangements of parts hereinafter described and claimed.-

w along the meeting edges thereof. Disposed eral type illustrated in my copending appli-' cation Serial No. 456,940 filed May 29, 1930.

' The hearth ring A comprises a lower inner ledge portion 1 and a higher outer rib portion 2, there being .an annular groove 3 in the face 4 or riser of the outer-rib 2 of said hearth ring A is ab electrode member 5 comprising a block of carborundum or other suitable refractory material conforming in shape to the face 4 of said rib 2 and having embedded therein a metallic conductor mem-* her .6 that extends through an insulator 7 that is disposed in a hole through the hearth ring A, the lower end of said conductor member 6 being provided with suitable nuts 8 for connecting it to the wiring system. The conductor member 9 for the other electrode C is likewise mounted in an insulator 10 which is secured in a hole in a lug 11 at the inner face of the inner or lower portion 1 of the hearth ring A. The electrode O forming the subject matte'r'o'ft-he present invention has a perforated end lug 12 by which it is secured to the top of the conductor member 9 as bya nut 13. This electrode C is a strip of heat resisting metal. Said electrode C has an upwardly curving portion 14 that extends from said lug 12 to the main body portion 15 of'the electrode. The main body 15 of the electrode (3 sl'opes slightly downwardly from said curved portion 14 and its outer end terminates a short distance away from the refractory block 5 to form a spark gap. The outertip portion 16 of the electrode G is shaped so that the arc will pass steadily between two points if there is no gas movement. However, upon movement of the surrounding at mosphere there will be a tendency for the arc to move along the top of the metal electrode and to wander over the surface oftheback electrode.' The somewhat blunt tip 16 serves to accentuate this characteristic. The upwardly curving portion 14 isprovided with a lateral extension 17, said extension being on the side toward the air spray. A notch 18 is formed at thejunction o the outer edge of'the extension with the main body of the electrode.

The portion of the electrode'in the vicinity of the spark gap and the gap itself, as well as .the groove 3, are located in a position that is normally rotected against air movements, the main ow of. air moving upwardly past the inner edge of the lower ledge 1 of the hearth ring (without entering the groove 3) and thence past the inner edge of top surface,

where it mlxes with the oil vapors arising from groove 3. Combustion then takes place entirely above the top of the segment. Inv

starting while the hearth ring is cold the rate at which the oil is vaporized in groove 3 is reduced and some combustion may take placefor a short period in this groove but the rate at which the vapor is evolved increases very rapidly and almost immediately the volume of vapor in groove 3 is so great as to preclude combustion due to a lack of air therein.

- Groove 3 therefore will normally serve to prointerference.

tect the gap against air currents, will surround it with oil vapor, and will-aid in rapid propagation of the flame from the region of the gap around the periphery of the hearth.

member.

A detailed explanation of the functioning tics discussed in my said copending applications are effective in producing a very effect1ve and successful lgnition system for the rotar type burner. However in some cases di culty has been encountered due to short circuitin of electrodes by carbon. Ordinarily thls was caused by improper oil quality, but in some cases it occurred where there was no defect in the oil. It was found that when the arc was-initiated with the electrodes thoroughly wetted with oil and with the are completely protected against air movement, a fine threadlike string of carbon might bridge the gap and extinguish the are. This threadlike structuremight have a diameter of not over 1/64 inch at the beginning of formation and apparently was instantly formed throughout its whole length upon initiation of the arc.

The tendency for this formation was mostnoticeable when the surrounding parts were cold. Ordinarily continuation of the current fiow through the stringy structure would soon burn it away and normal operation ensue but this was not always the case. Increasing the current flow tended to open the gap more quickly. Installingra condenser across the gap increased the frequency and the oscillating circuit had more beneficial effect. Increasing the length of the gap seemed to be most beneficial, but all of these methods had limitations or were impractical. Success agamst such 1n1t1al formatlon was obtained when the method explained below was adopted.

Complete protection of the gap against all air flow, while fundamentally proper, was not found to be essential in practice, while the scouring action of a small flow of oxidizing air redirected beneath thefiat surface of the electrode has most beneficialyand desirable effects. The electrode C is disposed substantially along the path of the air current, and this location together with the shape of the electrode serve to direct air towards the spark gap. The end portion 16 of the electrode C may be twisted so as to interpose a more extended surface in the air path immediatelyadjacent to the spark gap. The air d1rected.

to the vicinity of the arc serves to burn away i any carbon which might tend to collect from any cause, among which most important are the incomplete burning of poor grades of oil, the crackingof oil in the intense heat of the are, or the bridging action of stringy carbon structures described previously.

An added advantage resulting from the introduction of air to the vicinity of the spark gap exists when the burner is called upon to start with the hearth ring in a highly heated condition. Under such circumstances all of the oil discharged from the burner head a is immediately vaporized upon impingement against the hearth ring. The large volume of vapors released immediately fills the groove in which the spark gapcis located.

- As mentioned previously, during normal operation of the burner after the hearth ring has reached its operating temperature, the vapor in the groove is too rich for combustion which is limited to the area above'the ring proper. The same conditions exist upon restarting hot and unless provision is made for introducing excess'air at the gap, combustion does not take place immediately,

vapors fill the firebox and when ignition finally succeeds, an explosion may occur. However, by introducing an excess of air at the 7 gap, proper conditions exist at all times for prompt and reliable ignition.

While the air flow serves to burnaway any carbon collection. it has other beneficial effects of considerable importance without the detrimental effects which would be expected. The air flow tends to extend the length of the arc and because of the large area of one of the electrodes the arc wandersover a portion of this electrode. Such wandering of the point of are impingement eliminates any bad effects due to a slow building up of a pile of carbon as was sometimes noted when-the arc' remained stationary. The area over which the are wanders 1s not suflicient to reduce appreciably the heat concentration effect dis-- cussed in the earlier applications.

It might be expected that increasing the arc length by the methods discussed would result in a marked increase of radio interappreciable extent for several reasons. In

the first place the very high secondary current continues to maintain a veryv low gap resistance dueto the continued release of a large amount of heat. It has-also been found that the added flow of air past the gap prop er, while diluting the rich hydrocarbon vapors, does not displace them to any extent. The arc, therefore, continues to flow through the hydrocarbon vapors and maintains its characteristic intensely white and bushy appearance. This color is in contrast to the same arc in the open air with its flaming reddish color, and is evidently due to the presence of incandescent carbon particles released by cracking of thevapors due to the intense heat. Under these circumstances Iv have noted that the gap resistance is much less than the same gap in the open air. As any reduction in gap resistance is of importance in reducing radio interference this effect is very desirable and follows as .a direct result of my use of an intensely hot arc with its cracking effect upon the surrounding vapors.

' Much has been done by others working with ignitions of a somewhat similar type to reduce the effects of radio interference caused by their systems. Conventional methods such as the use of condensers across the windings, choke coil resistances .to reduce the flow of high frequencv currents in the high voltage having a sparking point located in a position normally protected against gas movement and deflecting means for directing an' air flow to the vicinitv of said sparking point. p

2. A spark igniter for oil burners wherein ignition and combustion take place at the outer peripherv of a hearth member toward which fuel and air are sprayed. said i gniter having a sparking point located in a position normally protected against gas movement and deflecting means on one electrode for directing an air flow to' the vicinity of said sparking point.

3. An electrode for snark tvpe ignition svstems for oil burners wherein ignition and combustion take place at the outer peripherv of a hearth member towards which fuel and air are sprayed, the spark gap being located I at a point protected from air movement, said electrode having a portion disposed in the path of air and shaped to intercept a portion of the air stream and direct it towards the spark gap.

4. An electrode for spark type ignition systems for oil burners wherein ignition and combustion take place at the outer periphery of a hearth'member towards which fuel and air are sprayed, said electrode comprising a thin strip having an upwardly'curving portion disposed in positionto intercept apart of the air stream and a body portion sloping combustion take place at the outer periphery of a hearth member towards which fuel and air are'sprayed, said electrode comprisinga thin strip "haying anupwardly curving por-. tion disposed in ,position'to intercept a part of the air stream and a body portion sloping downwardly from said curved portion towards the spark gap, the tipportion of said body being twisted to interposev an extended surface in the air current. i

6. A spark type ignition system for .oil burners wherein ignition and combustion take place at the outer periphery of a hearth member towards which fuel and air aresprayed, comprising an electrode disposed in the path of air and shaped to intercept a portion of the air stream and direct it towards the spark gap and having a blunt tip and a second electrode having an extended surface adjacent to' said tip.

7 An electrode for spark type ignition systems for oil burners wherein ignition and combustion take place at the outer periphery of a hearth member towards whichfuel and air are sprayed, saidv electrode having an upwardly curving portion disposed in position to intercept a part of the air stream and a body portion sloping downwardly from said curved portion towards the spark gap, said upwardly curving portion having a lateral extension on the side toward the air spray.

8. Inan oil burner of the type wherein oil and fuel are sprayed towardstheouter periphery of a hearth member, a stepped hearth ring having a lower inner ledge and a higher outer rib, with a depressed annular groove along the meeting edges thereof,.an electrode member in the face of said rib and a second sod electrode member having its sparking tip disposed in said groove so asv to be in a position normally protected against jar movement Lil.)

' electrode member in the a second electrode member having its spark- 1 hearth ring having a lower inner ledge and a higher outer rib, with a de ressed annular groove along the meetine ges thereof, an

-%ace of said rib and i'ng tip disposed in said. groove so as to be in a position normally protected against jar movement and having an upwardly curvin portion disposed in the path of air an shaped to intercept a portion of the air stream anddirect it towards the spark gap.

Signed at Detroit, Michigan, this 26 day of June 1931.

' V MILTON A. POWERS. 

